PROJECT SUMMARY The long-term goal of our laboratory is to contribute to our understanding of the interdependency between metabolism and transcriptional regulation, and to utilize this information to develop novel strategies for cancer treatment. Histone acetylation is a dynamic modification that affects chromatin structure and regulates diverse cellular functions, such as gene expression, DNA repair, and cell proliferation. Perturbation of the balanced action of histone acetyltransferases (HATs) and histone deacetylases (HDACs) alters the expression pattern of genes involved in cellular growth, resulting in tumorigenesis. Conversely, many HDAC inhibitors reactivate the transcription of multiple genes that are silenced in cancer and thus possess anti- cancer activity. Histone acetylation depends on intermediary metabolism for supplying acetyl-CoA in the nucleocytosolic compartment. Acetyl-CoA is thus a key metabolite at the crossroads of metabolism, chromatin structure and transcriptional regulation. We have shown that decreased synthesis of nucleocytosolic acetyl-CoA leads to histone hypoacetylation, decreased expression of histone genes, decreased nucleosome occupancy, globally altered chromatin structure, and altered transcriptional regulation. Our recent data have shown that decreased expression of histone genes or defects in nucleosome assembly result in increased mitochondrial activity and switch from fermentation to respiration. This represents a novel signaling mechanism, whereby decreased histone transcription and globally altered chromatin structure trigger mitochondrial respiration and increased synthesis of ATP. Since the two metabolic phenotypes, respiratory and fermentative, parallel the metabolic transition from respiration to glycolysis in tumor cells, analysis of the corresponding transcriptional mechanisms will inform studies of tumor metabolism. The central hypothesis of this proposal, based on our preliminary data, is that metabolism, through acetyl-CoA homeostasis and histone acetylation, regulates transcription of histone genes, which in turn regulates mitochondrial respiration. This hypothesis will be tested in two Aims that focus on the interdependency of chromatin and metabolism. In Aim 1, we will determine the mechanism through which acetyl-CoA regulates transcription of histone genes. In Aim 2, we will determine the mechanism through which decreased expression of histone genes induces mitochondrial respiration. Since both metabolism and epigenetic regulation of transcription are targets for cancer therapy, analysis of the regulatory links between metabolism, chromatin structure, and transcription will contribute to the identification of novel targets and approaches for cancer treatment. In addition, this project will provide an excellent research environment for undergraduate and graduate students as they prepare for careers in biomedical research.